The influence of additive content on microstructure and mechanical properties on the Csf/SiC composites after annealed treatment

•The addition of the chopped carbon fiber improved fracture toughness of the Ccf/SiC composites.•The appropriate proportion of La2O3 and Al2O3 would improve the wettability of SiC grains.•The in situ SiC nanowire after annealed treatment increased the mechanical properties.•Whisker pullout and nanowire bridge were the main toughened mechanics for Ccf/SiC composites.

In this paper, micrometers long and 20-100 nm diameter SiC nanowires had been synthesized in the short cut fiber toughened SiC composites (Csf/SiC) by annealing treatment. The present work demonstrated that it was possible to fabricate the in situ SiC nanowires toughened Csf/SiC composites by annealed treatment. The “vapor-liquid-solid” growth mechanism of the SiC nanowires was proposed. The mainly toughened mechanism concluded grain bridging, crack deflection, fiber debonding and SiC nanowires, which can improve fracture toughness.